Pardon my ignorance as I'm very new to this. I purchased a China knockoff of the Uno on eBay and found out after receiving it that it has the ATMEGA8A-PU chip on board. As I understand, this is a very old chip and I figure that this is probably the source of my problem. Also, the board looks nothing like a Uno - It has different connectors and an extra one with 10 pins and two buttons that I don't think the real Uno has. I'll try to upload a picture of the board.I downloaded the Mac Arduino software (1.0.5) and it seems to work correctly on the Mac. Through Arduino's "Tools/Board/" I set the board selection to "Arduino NG or older w/ATmega8". When I go to the Tools/Serial Port my options for ports are few. There are three like "/dev/ttu/Bluetooth-Incoming-Port" and a couple that have my phone name in the path. None have the term "usb" in it. Bottom line, I get the error "avrdude: stk500_recv(): programmer is not responding" and nothing happens.I researched several places and found a reference to having to load drivers which I did a couple of times. It didn't seem to make any difference. I went to another site that had me run some kind of code in the terminal window (I was a little uneasy about doing this!). I ran the process and saw no change. I've since ordered a different board but I really would like to see this board work. I've restarted several times and tried all of the different board selections. The board just doesn't seem to be recognized by the Mac. I saw a few comments suggesting that Mavericks is a problem but I can't help but think that this would be a hot item on the forum if this was the case. Anyone out there have knowledge of this problem? Thanks and my apologies if I've placed this in the wrong location.

Thanks for the followup greybruce. I bought an Arduino Uno on ebay from China too. I didn't realize it was knock-off and thought it was just a kit put together in China. I cannot get mine to recognize the USB port after many attempts and reading lots of troubleshooting. I'm going to contact seller as well and buy one locally. Should have known better.

I wonder how many people who are posting USB serial port issues bought theirs from China too. Might save a lot of trouble if people listed where they purchased there's.

Thanks FJ40 for the support. I'm with you on this. I hope you have better luck than I did. I didn't ever get any support from the seller. All I really know is that the seller went by the name of "email-for you" on eBay and they have a good rating. This was my first board and not knowing any better was duped. This family of devices looks to have a great deal of potential. I'm hoping to be a part of the "ground swell" of people taking advantage of them and creating some real impressive stuff. Take care

I bought another Arduino Uno from Radio Shack. Was acting the same way. Found a USB cord in my office and then they BOTH worked. So, the USB that was shipped to me was bad. The seller in China was great and offered to send me another one, but they are cheap, so I declined. Now I have two Arduino Uno's.